The present invention relates generally to a setup and wear determination procedure and apparatus for a sheet decurler in an electronic reprographic image forming apparatus. The invention is particularly adapted for use and will be described in connection with the setting up and wear monitoring of a decurler that decurls paper or other image recording sheets by passing same between a relatively soft elastomeric roll and a relatively hard pinch or penetrating roll. Those of ordinary skill in the art will recognize that the invention has broader application, and it is not intended that the invention be limited to the particular environment disclosed herein. The invention has application to any nip-forming device including a pair of parallel rollers that must be precisely positioned relative to each other, and the rollers can also be equally hard or soft.
It is generally known to pass a sheet of paper or another image recording sheet through a nip defined between a relatively soft roll and a relatively hard roll (the hard roll is referred to herein as the pinch roll or penetrating roll), and to control the amount of sheet decurling by controlling the degree to which the pinch roll penetrates into the associated soft roll. In modern high-speed image forming apparatus, decurling assemblies of this type must be adapted for rapid and accurate adjustment of pinch roll penetration. Furthermore, even extremely small variances in pinch roll penetration can alter the amount of decurling. In one modern image forming apparatus, the entire penetration range, from a simple paper transport position (no sheet decurling) to a maximum decurling penetration (maximum sheet decurling) is encompassed by only 0.5 millimeters (mm).
Unfortunately, in manufacturing the pinch roll, the soft roll, associated mounting components, and the other components used to control the position of the soft roll relative to the pinch roll, and also in assembly, dimensional tolerances on these components "stack-up" and require a decurler setup procedure so that penetration amounts can be accurately controlled. That is, the position of the soft roll relative to the pinch roll must be exactly known in order to adjust same accurately to achieve the desired pinch roll penetration.
Furthermore, the soft roll is typically manufactured using an elastomer or the like, and abrasion caused by the driven pinch roll and by the sheets, themselves, results in significant wear. Without a periodic decurler setup procedure, the soft roll wear would quickly result in penetration errors and, ultimately, early replacement of the soft roll. Furthermore, a need has been identified for a method and apparatus for assessing the wear rate of the soft roll so that its eventual exhaustion can be predicted to an operator of the image forming apparatus so that a service call can be scheduled in advance.